1. Field of the Invention
The present invention relates to a method of reading an image. It particularly relates to a method of preparatory scanning by a one-dimensional image sensor for reading a two-dimensional image such as the original image on a film, paper or the like.
2. Background of the Invention
There are known copying machines, a facsimile apparatus and so forth which are used as conventional image readers. A microfilm reader has recently been developed for an image processing system, to which it is preferable to apply the present invention.
The number of originals, in which various pieces of information are recorded, has been sharply increasing along with the general increase in the quantity of information these days. A system is strongly required nowadays in which a large number of such originals are stored in a compact space and can be easily retrieved. In order to meet the requirement, the information recorded in each of the originals needs to be compressed and then recorded by some means for storage. A microfilm, an optical disk or the like is used as the storage means. On the microfilm, two-dimensional visible information is recorded. Microfilm has advantages in that it can be preserved for a long period of time and can be used as legal evidence. Also, the same information can be copied a large number of times. The optical disk has advantages that a large quantity of information can be recorded therein, the addition or renewal of information can be performed on a real-time basis, and information recorded in the disk can be directly utilized for communication through the connection of the disk to a computer because the information is digitally recorded in the disk.
In order to make the most of the advantages of both the micro-film and the optical disk, it has been proposed that originals on paper or the like are sequentially photographed on the microfilm, and the information thus recorded on the microfilm and retrieval information for enabling future retrieval are recorded together on the optical disk. If the information on the originals and the retrieval information are thus recorded together in the optical disk, anyone can take out the recorded information, print it out, copy it on another microfilm or directly transmit it to a remote place through a facsimile system, when necessary, thus enabling the efficient utilization of the information.
FIGS. 2, 3 and 4 show block diagrams for describing an example of a microfilm reader for an image processing system which has been proposed for the purpose of writing information from an original into an optical disk. The microfilm reader is hereafter outlined with reference to FIG. 2. First, information on an original such as a character and a drawing or digital image information recorded in a computer memory is recorded on a microfilm. Then, only a desired piece of the information recorded on the microfilm is read by a microfilm scanner so that the read information is stored in the optical disk. For example, image information on the original 10, such as paper or the like, is photographed on the microfilm 40 by a microfilm photographing unit 20 (hereinafter simply referred to as camera). Conventional development 30 is then performed on the microfilm, as shown in FIG. 2. The microfilm 40 can be a 16-mm roll of microfilm 42, a 35-mm roll of microfilm 44, a microfiche 46, an aperture film 48 or the like. The image information recorded on the microfilm 40 is read by the microfilm scanner 100 so that the information is converted into digital image information PS. The information PS and control information, which is used for causing correspondence to the order of photographing of the photographed images, are sent to an optical disk recorder 200 in which the image information PS and the control information are stored on an optical disk 50. In order to read the information PS, the microfilm 40 is loaded in an exclusively used holder 102 and set in a prescribed position so that the microfilm is scanned by an image scanner 104 and converted into a digital signal. The image on the microfilm 40 can be projected on a screen 106 to perform the digital conversion while, if necessary, the projected image is being watched. When the image information PS has been recorded in the optical disk 50 through the optical disk recorder 200, the image information PS inputted through the scanner 202, is read and the image is shown on a CRT display unit 204. Then index information for indicating the contents, kind or the like of the image is inputted through a keyboard 206 while the image shown on the display unit 204 is being watched. The inputted index information is written on the optical disk 50. Otherwise, the index information may be inputted through the keyboard 206 while the image projected on the screen 106 of the microfilm scanner 100 is being watched. Usually, such input work in done by a single operator. It takes 8 hours for him to process about 3,000 pages of originals. In order to increase the speed of the input work, a personal computer system 60 may be provided to do the work. In that case, a plurality of personal computers 62 and 64 are installed. The index information is inputted into one computer 62 through a keyboard 62a while the image projected on the screen 106 of the microfilm scanner 100 is being watched. An exclusively used microfilm reader 100a is provided for the other computer 64 to input the index information through a keyboard 64a while the image on the screen 106a of the microfilm reader 100 is being watched. Thereby, the information is written into both floppy disks 66 and 68. The floppy disks are put in the floppy disk section 70 of the optical disk recorder 200 to read data to write the index information onto the optical disk 50 correspondingly to the image information stored in the optical disk 50. It can be made possible that the index information created by the personal computers 62 and 64 are inputted into and outputted from the microfilm scanner 100. This techniques provides the scanner with a retrieval function to transfer to the optical disk recorder 200 the index information together with the image information and the control information.
The constitution of the microfilm scanner 100 is hereafter described with reference to FIG. 3. The microfilm scanner 100 comprises chiefly an optical reading section 120 for reading the image information on the microfilm, a section 140 for driving the optical reading section 120, a signal processing section 160 for supplying a read signal from the optical reading section 120 to the optical disk recorder 200, and a control section 180 for controlling the driving section 140 and the signal processing section 160.
The optical reading section 120 includes an illuminator 122 including a light source 1222 and a condensing lens 1224, a microfilm holder 124 which sandwiches the microfilm 40 between tight contact glasses 1242a and 1242b in order to prevent the image from being distorted. An image projector 126 in the optical reading section 120 includes a projecting lens 1262, focusing lenses 1264 and 1266, a half mirror 1268, which divides rays of light, and the screen 106. A feed reel 128a and a winding reel 128b move the microfilm 40 into an illuminating optical path. A mark sensor 130 optically detects a blip mark provided on the microfilm 40 or detects the difference in density between the frame and the space of the adjacent frames of the microfilm 40. An automatic exposure control sensor 132 detects the density of the microfilm 40 to read the image under optimum conditions. In a sensor unit 134, the optical image projected by the half mirror 1268 is scanned by the image sensor 104 so that the image is converted into an electric signal. If an image sensor is used which can read an image enlarged to the size of the original before the reduction of the image to a microscopic image, the focusing lenses 1264 and 1266 are not required.
The driving section 140 comprises a driving controller 144 for driving the feed reel 128a and the winding reel 128b depending on a signal from the mark sensor 130 to move the frames of the microfilm 40. In the driving section 140, a driving circuit 150 controls a motor 148 for driving a screw-nut mechanism mechanically coupled to the image sensor 104. As the motor 148 is rotated, the image sensor 104 can scan a surface around an optical axis.
The signal processing section 160 comprises a read-driving circuit 162, a resolution changeover circuit 164, and an RS422 data port 166. The read-driving circuit 162 functions to appropriately move the image sensor 104 to perform focusing, on the basis of the film density measured by the sensor 132, in order to read the image under the optimum conditions. The read-driving circuit 162 functions to supply the resolution changeover circuit 164 with the image information obtained by detecting the image through the image sensor 104 and by subjecting the image to photoelectric conversion. The resolution changeover circuit 164 sends out the image information at an optional line density such as 16 lines per millimeter and 8 lines per millimeter to an optical disk recorder 200 through the RS422 data port 166.
The controller 180 is a circuit for controlling the driving section 140 and the signal processing circuit 160, and comprises a central processing unit (hereinafter referred to as CPU) 182, an RS232C data port 184 for transmitting the control information, the image information and so forth between the CPU 182 and the optical disk recorder 200. It further comprises a personal computer 186 for transmitting a command to the CPU 182 through the RS232C data port 184. The controller 180 controls the driving controller 144 and the driving circuit 150 in accordance with an instruction from a keyboard 188 through an interface 190 which imparts another command to the CPU 182.
The constitution of the optical disk recorder 200 is hereafter described with reference to the block diagram of FIG. 4. The disk recorder 200 comprises a CPU 210, a read-only memory (ROM) 212, a random-access memory (RAM) 214, a cathode-ray tube (CRT) 216, a keyboard 218 and an interface 220, which are connected to a common bus 222. The interface 220 is also connected to a floppy disk unit 70 or a host-side CPU 224.
A graphic processor 228 performs the compilation, addition, elimination, enlargement or reduction of an image. The graphic processor 228, scanner 202 and the microfilm scanner 100 are connected to the CPU 224 by a bus 226.
A write or read controller 240, which controls the writing and reading into and from a floppy disk, and a driving section 260 are connected to the CPU 210, the ROM 212, the RAM 214, the CRT 216, the keyboard 218 and the interface 220 through an interface 230 and a bus 232. In the write or read controller 240, the writing of the image information and the reading of the stored image information are controlled by a disk data control section 242. The writing is performed by generating a laser beam LB from a laser driver 246 through the operation of a modulator 244. This operation depends on the image information, the control information and the index information and by the microfilm scanner 100 and the scanner 202.
Reading from the optical disk 50 is performed by a photo-cell 250 coupled to a reading head 248. Information optically picked up by the photo-cell 250 is transmitted through a photo-cell processor 252 and then demodulated by a demodulator 254. The reading head 248 is positioned by a focusing mechanism 256 to focus on the line of pits on the optical disk 50 to precisely read the information through the photo-cell 250.
The driving section 260 consists of a sector control system 262 and a cross feed control system 272. The sector control system is supervised by a sector controller 262. The cross feed control system is supervised by a cross feed controller 272. The sector controller 262 controls a spindle motor 266 through a driver 264. An actual controlled position is detected by a sector wheel 268 and a sector pulse counter 270. Data on the detected position is fed back to the sector controller 262 to control the spindle motor 266 to an instructed position for a sector. The cross feed controller 272 controls a linear motor 276 through a driver 274. The controlled position of the linear motor 276 is detected by a Moire fringe 278 and a grating 280. Data on the detected position is fed back to the cross feed controller 272 to control the linear motor 276 to an instructed for cross feed.
If the above-described microfilm reader is used, not only existing information provided on a microfilm but also other information not provided on the microfilm but appropriate to be recorded in the optical disk can be provided on another microfilm and stored, and the stored information can be retrieved and utilized in an on-line manner. In the microfilm reader, as shown in FIG. 5, the microfilm 40, which is projected on an exposure table 1342 by illuminating light from the light source 1222, is scanned by the linear image sensor 104 in a main scanning direction X along the array of the sensor and in an auxiliary scanning direction Y in which the sensor is mechanically driven. Each element of the linear image sensor 104 at each scanning position constitutes an image element matrix along the two dimensions X and Y. As a result, an image signal is obtained from the sensor 104 in a time-serial manner for each image element and converted into a binary signal which is outputted for later processing. The main scanning action of the one-dimensional image sensor 104 is electrically performed only in a forward direction through the read-driving circuit. The auxiliary scanning action of the sensor and its return scanning action to a reading start position performed through the mechanical reciprocating action of an auxiliary scanning mechanism.
FIG. 6 shows a schematic view of the auxiliary scanning mechanism of the microfilm reader. Differently from the screw-nut mechanism 146 shown in FIG. 3, the rotative power of the pulse motor 148 is transmitted by pulleys in the auxiliary scanning mechanism to reciprocate the image sensor 104. The rotary motion of the driving shaft of the pulse motor 148 is transmitted to a pulley 624 through a pulley 620 and a belt 622, and then transmitted to cables 630a and 630b or the like wound on pulleys 628a and 628b, through the shaft 626 of the pulley 624 and the pulleys 628a and 628b provided at both the ends of the shaft 626. An auxiliary scanning support 632 is coupled to the cables 630a and 630b. The linear image sensor 104 is secured to the auxiliary scanning support 632. One end of the support 632 is movably attached to a fixed guide 636a through a movable guide 634, while the other end of the support 632 is movable on another fixed guide 636b. In the auxiliary scanning mechanism, the pulse motor 148 can be rotated forward (in an auxiliary scanning direction) or backward (in a return scanning direction) to cause the image sensor 104 to perform the scanning. A driving circuit 150, as shown in FIGS. 3 and 7, for driving the pulse motor 148 includes a section 150a for driving the motor and a pulse generator 150b for supplying the driving section with pulses for controlling the driving.
As shown in FIG. 8, when each single image 300 is to be read by the linear image sensor 104, the sensor 104 is mechanically drive in the auxiliary scanning direction to perform preparatory scanning simultaneously with the electric scanning in the main scanning direction. The sensor 104 is thereafter returned from a preparatory scanning end position Q to the read-scanning start position P. The preparatory scanning measured reading conditions such as the density of the image and its contrast. Under the reading conditions measured by the preparatory scanning, the image sensor 104 is caused to perform major scanning to read the image. The image sensor 104 is thereafter returned from the scanning end position Q to the scanning start position P. For that reason, in such a conventional image reading method, the image sensor is reciprocated twice, the first time for the preparatory scanning and the second time for the major scanning. Therefore, it is time-consuming to read each single image. Because of the double reciprocation of the image sensor to read each single image, the frequency of operation of the auxiliary scanning mechanism is so high that its life is shortened. Since a means for quickly returning the image sensor is needed, the circuit constitution of the auxiliary scanning mechanism is complicated and expensive.